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What is the motivation behind designing a control stick that does not move?
According to Wikipedia (and various other online sources), the control stick on the F-16 does not move. The input values are determined by the amount of force acting on the stick, rather than the deflection angle/distance away from its neutral position like the majority of sticks and yokes. After pilots reported the design as "unnatural", the stick was modified so it would move a little.
Clearly the designers must have thought that having a very stiff control stick is advantageous. Why?

And I thought Airbus sidesticks were bad. I cannot imagine a worse way of controlling an aircraft.

@Bianfable, wait until they come up with a virtual joystick on a touchscreen... ;)

@bogl We've come quite advanced in material engineering that we don't have to worry about a control mechanism wearing out. Steering wheels in cars are not falling off any moment!

Never underestimate the requirements on a mechanism inside the cockpit of a jet fighter. However, it was a comment, not an attempt to answer. I don't know why you compare with a steering wheel in a car, but feel free to have a look at https://www.motor1.com/news/185032/nhtsa-investigating-ford-steering-wheels/ .  ;)

@kevin i heard a story about a car steering wheel coming off when the owner is in love motel. His wife is not happy about that.

The short answer is because airplanes are designed by engineers, not pilots.  Engineers don't always think like regular folks!  ;)

It's more of less like riding a motorcycle, that the motion of the handle bar doesn't matter (nobody pays attention, and it moves counter-intuitively) and it's more of the force that give the rider the feedback.

The F-16 side stick was ultimately revised to include approximately 1/4 inch of travel IIRC.

@Bianfable try flying in FlightGear with only a keyboard and mouse (I assume any sim would be as bad)

The stick does not need to move in order for the pilots to sense their inputs!
Humans have very accurate force sensors in their fingers, and no direct position sensors. Proprioception provides positional information as @aroth mentions in a comment, however it is based on muscle tone sensing - force detection. The hand is at the end of a 5-DoF arm, with serial accumulation of measurement errors. Meaning that without looking, we only have a general idea where our hand is due to muscle tone sensing, but we don't need to look at our hand to know exactly how hard it is pushing at an object due to the force sensors in the skin of the fingers. For the human, force is the imminent control feedback factor.
The F-16 can do 9G in manoeuvres, and the pilot is inclined backwards with their arm on an armrest. If this arm needs to move a stick it shifts position, and during a manoeuvre can get grabbed by the load factor - precise control is much easier if the hand, wrist and arm can stay in one position.
A pilot who has flown both the F-16 and the centre stick F-18 has this to say about it:

Flying a side-stick control takes a while to get used to, but once you do, it's a joy. The conformai stick's shape feels very natural (it fits in the hand like a melted candy bar), and it allows easy access to nine of the 16 hotAS controls. Two fully adjustable forearm rests on the right cockpit bulkhead stabilize and isolate the pilot's arm and wrist, so when rattling around the cockpit during turbulence or going after the bad guy, the pilot's arm won't accidentally move and initiate unwanted control inputs.

Initially the stick was fixed completely and pilots would get comfortable with the novel concept of no stick movement pretty quickly. But there were two issues:

Cross-coupling. The control input must be separated in two axes, pitch and roll, and this is difficult to separate if feedback is from force only. In order to aid this, a small bit of movement was introduced with a breakout force in the centre: upon release, the stick moves back to neutral and requires a bit of force to be deflected from there. From the article linked above:

However, after initial F-16 flight tests, a ¼ inch of stick movement was incorporated to give a small dead band and a nominal breakout force to give better "feel" of a neutral stick because otherwise it was entirely too sensitive. The control harmony is quite good (the pressures required for pitch and roll mix well), but without the capability to physically position the stick, it's easy to contaminate roll inputs with unwanted pitch inputs, and vice versa

When the sticks were fixed, F16s kept getting back with bent sticks. During chasing another plane and pulling, pulling on the stick, they pulled excessively hard while the fly-by-wire was already generating the deflection for maximum load factor. With the stick now moving a little bit, the pilot can feel that the limit is reached when hitting the travel stop at 25 lbs. At this force the acceleration is 9G and pulling harder has no additional effect. (As explained during the course of Human Factors at uni.)

Given you last sentence, I can't imagine the adrenaline level during dogfight: maximum load factor and the pilot pulling hard to exceed that value.

@ManuH 25 pounds is just 11kg. It's not little, but it's very achievable. I regularly carry six-packs of mineral water (6x2 kg), so hitting the travel stop should be no issue for any decent pilot. I don't know how much extra tolerance is there, but it shoudn't be that hard to bend the stick.

@JohnDvorak I thing you misunderstood. I meant the pilot is already experiencing a load factor of 9g and is still pulling to turn tighter.

"Humans have very accurate force sensors in their fingers, and no direct position sensors." - Not entirely true.  We have a sense of proprioception.  The methods by which the body senses/reports proprioception are not dissimilar from how it senses/reports direct contact, so I'd be hesitant to dismiss the information as "very vague" (or even as less valuable/clear than touch/force feedback). Certainly I can close my eyes and have no difficulty determining how my arms, wrists, and hands are currently positioned through their entire range of motion.

When I was recently selling an aircraft with a sidestick controller, I was demonstrating a side slip to the prospective buyer, and inadvertently broke the stick off near the root. It was surprising how you can underestimate the force you can put on the flight controls. (It was [No] fun flying the thing back to the field by grabbing the remaining inch and a half of stick linkage that was still connected...

With a deflection-sensing (conventional) stick, it takes a certain time to move the stick. If you're trying to do quick manoeuvres going from (say) full nose-up to full nose-down deflection, that fraction of a second can be a significant delay, especially in a fly-by-wire aircraft with powerful, fast-acting actuators. With a force-sensing stick, that delay is removed. Force-sensing sticks also cause less arm fatigue.
Others have pointed out that force-sensing sticks are also mechanically simpler, because of the lack of moving parts. This seems like a small concern, but for military aircraft, which get more frequent inspections and have a very stretched-out supply chain, removing any need for a replacement part can be a big benefit. It's the kind of design criterion where, even if it isn't really a huge factor on this aircraft, an engineer who was burned by a spares or inspection problem on a previous design might consider that a big project risk.
The mechanical simplicity can also make the extra buttons etc. on the stick more reliable, because there doesn't need to be wiring through a rotating joint, which might get trapped or wear insulation. And the fact you don't need space for the stick to move can make it easier to design other components around the stick.
As this project found, the chief downside is that force-sensing sticks are unfamiliar to most pilots, and they take a lot of getting used to. They also make training harder: with a deflection-sensing stick, it's easy to show a student pilot the appropriate stick position for a particular manoeuvre (e.g. to show the progressive pulling back in the flare). This is much harder with a force-sensing stick. Obviously, pilots won't be doing their initial training on this aircraft, but they still need to demonstrate handling characteristics etc. when familiarising on type.

The motivation is the same, albeit for stronger reasons, as that for the 1960's Citroën DS's brake button or frein champignon, which responded to foot pressure rather than foot travel.  Namely, faster response, to take advantage of the 2500 psi hydraulics in this unorthodox and quite fast car.  Moving your toe half an inch instead of your leg half a foot (ahem) can seriously shorten your braking distance.

ALL brakes respond to pressure rather than travel. The only difference was shorter travel, which indeed can lead to faster response. But the motivation for aircraft is deeper than that.

Of course.  Even bicycle brakes apply more force with more pressure, obeying Hooke's law.  For aviation, which deeper motivation do you mean?

Dynamics and kinematics of flight control is more complex. (For brakes, the effect simply depends on the pads pressure). Traditionally (mechanically), actuation is by position, but the effect strongly depends on airspeed. In reversible control (light airplanes), stiffnes changes accordingly, which gives an effect of force control. But with irreversible control this effect is lost, and one needs to design workarounds like variable control stiffener or ratio. Instead, why not just sense force? (Why force and not position is covered in Koyovis' answer; we humans are just better at sensing it).

I’ve owned a Citroen GS when in uni, was fascinated by the demo of hydraulic suspension. It worked great, and at traffic lights could keep entertained by moving the car up & down. But once when driving late at night to a town 300 km away the hydraulic fluid warning light came on, and the car barely made it, was pretty comcerned and no petrol stations were open. An important lesson on passive safety of systems, the hydraulic system powered the brakes as well.

It does move. The F-16 Side Stick Controller has always measured displacement. The YF-16 prototype had a much smaller displacement than production F-16s, but it still moved.
The small throw of the stick allows a much smaller controller that saves weight over direct linkages. Also, stabilizing the arm on the rests and flying with the wrists requires less elbow room in the tight cockpit of what was originally a light daylight fighter. Ergonomically it reduces fatigue by employing smaller muscle groups during basic fighter maneuvers. Designwise, there is stiffer structure on the side of the cockpit than up from the floor in the center console to attach it.
The ultimate loads required to break a side stick are over 300 lbs. No one has ever broken one inflight.
As an engineering principle, you can’t measure force. You measure displacement against a linear spring force - like a fish scale. The side stick uses multiple linear transducers in two axes to measure displacement. Always has.

You can measure force, this is how control loading systems in flight simulators work. Strain gauges measure force from the stretch in the metal they’re attached to - which does affirm your statement, granted.

You aren’t measuring force directly, you are measuring displacement against a linear spring force; whether it is a spring or a bending beam. It is a calculation. Even with a strain gage, the beam has to bend. “Stretching” is displacement.  Strain gages are used in simulators and gaming but they are not used to fly a plane.

It sounds like you might have been involved in the design of the aircraft.  Thank you sir!  The F-16 was a joy to fly.  My only complaint was the AOA limiter.  I think it was 25 degrees, which is not nearly enough in a slow speed fight.  I suppose it's a moot point now with modern weapons, though.

The AOA limit wasn’t for lack of effort and resources.

The F-16 was the one of the first production "fly-by-wire" planes without direct mechanical linkage between cockpit controls and aerodynamic controls. The development of electrical-output pressure sensors made it possible to do things a different way.
Why have the weight, mechanical complexity, cost and maintenance overhead of hinges and stuff when you don't need them?
Turned out some movement is required to provide pilot feedback, but the principle remains.

By no means was F-16 the first FBW. Also, its FBW (as well as pressure sensors) were originally analog. Finally, FBW can be made position-sensing with just the same weight and mechanical savings (e.g. Concorde - which also predates F-16), and the question was why even attempt to do force-sensing.

Thanks, well spotted. Now added/corrected. But Concorde is a bad comparison and the savings on the stick and rudder pivot mechanisms remain.


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Why are the toggle switches in cockpits of new aircraft painted white?
The toggle switches in the cockpits of new aircraft are painted white. e.g. 737 MAX:

but a 727

Why?

I wouldn't necessarily call the 737 a new aircraft. It first flew in the 60s and the design of the overhead has not changed since then (including for the MAX). Check out pictures of the 777 and 787 for the new design used by Boeing.

The reason is threefold:

White knobs offer better contrast, and are thus easier to spot regardless of lighting conditions

The material used has improved and consistent friction and "feel" to it. Bare metal switches, especially when worn out by use may become slippery, and since some of the toggle switces have detents, operating them might be compromized.

The plastic coating (on at least most) of the switches can be renewed without replacing the whole switch assembly. For example on the larger switches white knobs are screw on -type

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When pilots check in with a different controller, how to reference flight level?
When pilots check in with a different controller after they are handed off, how do they report their current altitude in flight levels if they are in level flight or a climb / descent? I feel like saying "level flight level" could be misunderstood.
Can pilots omit the "flight level" phraseology in the examples below?
"(ATC Facility) Baron x-ray five x-ray sierra level flight level two-five-zero... " (level flight @ FL250)
"(ATC Facility) Baron x-ray five x-ray sierra flight level two-five-zero climbing flight level three-two-zero..."
"(ATC Facility) Baron x-ray five x-ray sierra flight level two-five-zero descending flight level two-zero-zero..."

You didn't say which country you're interested in, but in the US the standard phraseology is indeed to use "level" twice. This is from the AIM 5-3-1:

When operating in a radar environment: On initial contact, the pilot
  should inform the controller of the aircraft’s assigned altitude
  preceded by the words “level,” or “climbing to,” or “descending to,”
  as appropriate; and the aircraft’s present vacating altitude, if
  applicable
EXAMPLE −
  1. (Name) CENTER, (aircraft identification), LEVEL (altitude or flight level).

Per 4-2-9, the correct way to state a flight level is:

At and above 18,000 feet MSL (FL 180), state the words “flight level”
  followed by the separate digits of the flight level.

So put all that together and you get something like this:

Indianapolis Center, N12345 level flight level 210

Practically, I hear a lot of pilots omit the words "flight level", perhaps because they seem superfluous:

Indianapolis Center, N12345 level at 210

As for misunderstanding, personally I think that's unlikely even if you use the word "level" twice. A flight level is stated as three digits ("two one zero") whereas an altitude always includes the units, i.e. thousands and hundreds ("five thousand five hundred").

The reason to state the altitude on initial contact with a facility is to VERIFY that what the controller is seeing is accurate -- which it is 99.9% of the time. So if you're level, he knows that & can see that because your altitude block isn't changing. So the salient point being communicated is the "210" part. I'd always include "flight level" since 210 can also be a heading, or an airspeed. But "level" is often omitted -- "Center, N12345, flight level 210" communicates everything the controller needs, without the messy "level flight level" phrase.

I was listening to a liveatc.net broadcast and heard "level flight level", and accepting this as the answer since it's backed up with a reference.

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Is ATC clearance or permission required to fly helicopter routes and transitions in the Los Angeles area?
Skyvector has Los Angeles helicopter charts here and here.
Are pilots required to obtain ATC clearance or permission to fly helicopter routes and transitions?

According to the FAA's JO7210.3AA Facility Operation and Administration (chapter 11, section 5):

Pilot adherence to charted helicopter routes and the recommended
  altitudes or flight ceilings associated with them will normally be
  voluntary. However, controllers may assign charted routes and
  altitudes and expect or request pilot compliance with them, provided
  such procedures are called for in specific FAA−operator Letters of
  Agreement, or are necessitated by traffic density and/or safety
  considerations; controllers also may restrict operations within
  designated operating zones when requested by local law enforcement
  officials and the restriction would not adversely affect other
  aircraft operations.

In other words, it's mostly a voluntary thing but pilots should still be aware of them and prepared to follow them if instructed.
And you have to consider the airspace as well: large parts of some routes are in uncontrolled class G airspace, e.g. the PALISADES coastal route, west of Santa Monica. ATC doesn't control traffic in class G, so asking for permission wouldn't make sense.

@jeff0000 Oops, I added the missing chapter to the answer. Thanks for pointing that out!


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If a SID chart says "GPS... required", can the plane use a different GNSS?
This US/FAA standard instrument departure says "Note: GPS or DME/DME/IRU required."
If the aircraft could tune into a different GNSS like GLONASS, could the pilot still legally fly the departure given that all other requirements were met?

The FAA's standards require the use of GPS, i.e. the American satellites. This is covered in AC 20-138D, Airworthiness Approval of Positioning and Navigation Systems. It defines GPS:

k. Global Positioning System (GPS). GPS is a U.S. satellite-based radio navigation system that provides a global positioning service.

It also says that GLONASS and other non-US systems are not supported:

GLONASS is not yet approved for IFR operations in the U.S. National
Airspace System
[...]
No FAA TSO exists for GLONASS, GPS/GLONASS, multi-constellation or
dual-frequency avionics. Therefore, adding capability for any other
constellation or dual-frequency capability must be accomplished as a
non-TSO function until appropriate TSOs are available.

Apparently there is some kind of working group looking into using non-US GNSS but it's not possible yet. See Appendix 8 of the doc for full information.


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What makes a visual approach quicker than an ILS approach?
In the question What's the preferred approach for a passenger jet? it is mentioned that pilots prefer Visual Approaches over ILS Approaches, as they are a lot quicker.
Why would a visual approach be quicker than an ILS approach?

Here is a cockpit video with an example of a visual approach that might be useful to you. It is annotated with information about why the visual approach is preferred in this case.

Visual approaches can be conducted from any point around the airport where the runway is in sight, e.g. if you are approaching from the north of the airport, you can be vectored to a position which is closer to the airport and be cleared for a visual approach from a position where you can turn visually and reach the runway threshold.
ILS approaches begin at the approach gate before the final approach fix (FAF) for the localizer and glidepath indications to be correctly used and the aircraft configured for the approach. The FAF is at many airport around 10 NM from the runway threshold at 3.000ft AGL, thus placing the approach gate at around 12-14 NM.
A pilot on a forum has summed it up like this:

Visual approaches are usually shorter than instrument approaches. By that, I mean that the turn to final is accomplished closer to the runway when on a visual approach.
When traffic is heavier, or weather is around, or it's hazy, smoggy, etc, ATC will usually route everyone out for an ILS.
Many times, a pilot will call runway in sight, yet be sequenced behind someone who is on the ILS. So, he'll get routed out for an ILS approach, even though he'll go visual within the cockpit.
Airport size doesn't have a whole lot to do with it. Also, even though an aircraft may be on a visual approach, that does not absolve ATC of separation resposibility.

(Source: www.airliners.net - Author: Tom in NO)
Effectively, this means that visual approaches tend to be shorter and quicker than ILS approaches with vectors to the FAF/approach gate.

actually, when being vectored to final on an ILS approach, the aircraft is vectored outside the "approach gate", which is 1 - 2 miles before the FAF, depending on weather. http://www.terps.com/ifrr/feb98c.pdf

@rbp Correct. Did I say anything to the contrary?

"begin at the final approach fix". i was making the point that they effectively begin before the FAF, outside the gate, which makes the approach even longer

At the risk of just repeating information from the great answers that SentryRaven and casey already gave, here's a real example.
Last night I flew the ILS 22 into KLEX for practice, although conditions were perfectly clear and most aircraft were using a visual approach. If it had been a 'real' flight and not practice I would certainly have taken the visual as well because it would have saved almost half an hour of flight time (and fuel):

I was inbound from the west and ATC started vectoring me when I was still more than 10 miles from KLEX to get me onto the ILS approach. They sent me northeast, east then southeast to intercept the glideslope. That means that instead of just flying 10 miles directly to join the pattern, I was vectored for almost 40 miles. Normally, you just don't want to use up that much time and fuel if you don't have to. Unfortunately I don't have track data from the flight but it looked roughly like this; even if you aren't familiar with the chart you can probably see how using the ILS required a huge diversion. The pink line is my route and the red arrow shows where the vectors started:

I was cleared for the ILS while about 10nm from the runway. But the winds were very high, and instead of having a ground speed of 80 or 90 knots (in a C172), I had a ground speed of 50. That meant I took about 12 minutes to land, which effectively blocked the final approach course for that amount of time. A faster aircraft on a visual approach was turned in behind me and had to do S-turns on final to avoid getting too close. If I had been on a visual approach instead, I would have been in the traffic pattern very close to the runway and would have spent just a minute or two on final.

It's also worth noting that apart from flight time, another reason to prefer visual approaches is that a pilot (a private one, anyway) has a much lower workload. You don't have to brief the approach, set up your nav equipment (and maybe autopilot) etc.; instead, you just look outside and fly visually.

At what time UTC and possibly the callsign? FlightRadar24 should have your track if your are ADS-B out capable...

@SentryRaven Good idea! I found it but the track isn't complete and not very detailed. It does show that the vectoring started earlier and was much less abrupt than I put in my answer, but the end result is the same.

Visual approaches are preferred because it means you can potentially avoid being vectored out to intercept the final approach fix (FAF) which needs to be done for a an ILS approach.  If there is a long line of aircraft being vectored for the approach this may not yield any time savings as minimum spacing with the aircraft in front of you becomes a factor.  At an airport that isn't busy this can be the difference between flying a tight traffic pattern and landing quickly or a long vector 5+ miles past the airport to join the approach.
Also, being on a visual approach clearance with the aircraft in front of you in sight relieves the controller from providing normal spacing.  This means you can squeeze a bit closer to the airplane you are following and you just have to make sure you are keeping far enough back that the runway will be clear when you get to it.  This can also help if the airplane in front of you slows down unexpectedly or too early, which if you are on an non-visual approach could result in S-turns for you or a missed approach.  In these cases the controller often asks if you can see the aircraft so you can be given the visual clearance and manage the spacing yourself and avoid going missed.

Isn't the separation minimum also lower on visual approaches?

@TomMcW from my post -- "Also, being on a visual approach clearance with the aircraft in front of you in sight relieves the controller from providing normal spacing."

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What aerodynamic data (drag/lift curves) exists for the A-10?
This is one of 3 question in "series" - one question split up in 3 to better reward those responding about each aircraft. Other questions: Yak-131, L-159
A-10 is one 3 planes that are used in the ArmA 3 combat simulator, but its aerodynamics modelling currently lacks significantly. I'm planning on writing a short "essay" to developers regarding what and how can be specifically fixed in the flight model, but I'd like to back my research with some hard data. Specifically, I'm interested in any of the following:

L/AoA
D/AoA
Side lift/SA (Slide angle)
Max G/velocity
Flight envelopes (like one below for F-15):

Torques can well be left out - it's not a full fledged simulator, but the above data can give quite a good estimation of high level characteristics already.
Are there any good sources on any of the above data? I've found some (see below), but the quality leaves a lot to desire. Low-mach data is good enough for me.
I understand this is a tall order, but, well, SE is for expert answers - maybe a wonder happens and someone here has it? :)
What I've found so far:

Some superficial modelling of A-10
A-10 airfoil: NACA 6716 root, NACA 6713 tip
Set of A-10 documentation

Data like this is quite hard to come by. Civilian manufacturers of large aircraft charge simulator companies huge amounts of money (on the order of hundreds of thousands of dollars) for "data packages" that contain this stuff. It's going to be much, much harder to obtain similar data for military aircraft (no "need to know," and some of the data may still be classified).

On one side, yes. On the other side, the airframe is almost 50 years old, so it's not like it needs so much secrecy. Besides, there is a lot of educational material built on such famous and battle-proven aircraft usually. Similar F-15's data, for example, is circulating freely

You are aware that game physics and flight physics differ greatly, right?. Game physics must run in better-than real time; flight physics requires substantial mathematical effort to execute in real time.

I participated in the development of Rise of Flight sim, so yeah, I know that and I know how to model it.

Yes, any info would be valuable, thanks

A-10's don't need lift, Gravity is too scared to touch them :p

I'm okay with a plot of how scared it is depending on AoA

Lift and form drag you should be able to calculate quite accurately with inviscid CFD solvers, and then you have 1-3. Try using openVSP to model the geometry from 3-view drawings and then getting your hand on Cart3D (and let me know if you get your hands on it) to solve. Otherwise use xflr and just model the wings and tailplane, this should give quite accurate stability derivatives.  Flight dynamics is mainly dependent on form and induced drag, skin friction is however very hard to accurately estimate but it is not that important for flight dynamics.

Good luck finding number 1-3 on your list.  As far as I know these are proprietary data the you would have to get from Fairchild Republic.  After a career of flying fighters I never saw this data or really care about it.
In my opinions numbers 4 and 5 on your list are much more relevant.  What you are looking for are called EM diagrams.  EM stands for energy maneuverability and these diagrams show a scale of turn rate, turn radius, airspeed and altitude to display meanueverability at a given energy state.
Using these diagrams you can find some key performance factors:
Min maneuvering airspeed - where the rate and radius slope drops off on the left of the chard showing min flying airspeed at given altitudes and wing loading
Max instantaneous rate of turn - max possible turn rate given a certain energy state - top of the rate curve then drops off
Max sustained rate of turn - maximum rate that can be achieved while maintaining your energy state (Ps = 0)
Corner velocity - velocity to achieve max rate at a given energy state
Min radius - smallest radius of turn acheveable given a certain energy state
Radius for given conditions - important to determine this when planning something like a targeting attack
I've found an A-10 EM diagram and a good Mig-21 diagram that annotates the factors I have defined above.
Note:  I have to giggle at your "Low-Mach data is good enough for me" statement.  There is no high-Mach data in an A-10.  It will top out around .6 Mach (max speed around .7)
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In my opinions numbers 4 and 5 on your list are much more relevant. not if you want to simulate the aerodynamic behaviour (the stated goal behind the question)

Actually, without a full 6 degree-of freedom aerodynamic simulation, then programming the aerodynamic characteristics in the links he already has along with the realistic turn rate and radius limits from the EM diagram provided, he can get a realistic representation with normal gaming simulations

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What aerodynamic data (drag/lift curves) exists for the L-159 Alca?
This is one of 3 question in "series" - one question split up in 3 to better reward those responding about each aircraft. Other questions: A-10 Yak-131
L-159 Alca is one 3 planes that are used in the ArmA 3 combat sumilator, but its aerodynamics modelling currently lacks significantly. I'm planning on writing a short "essay" to developers regarding what and how can be specifically fixed in the flight model, but I'd like to back my research with some hard data. Specifically, I'm interested in any of the following:

L/AoA
D/AoA
Side lift/SA (Slide angle)
Max G/velocity
Flight envelopes (like one below for F-15):

Torques can well be left out - it's not a full fledged simulator, but the above data can give quite a good estimation of high level characteristics already
Are there any good sources on any of the above data? Low-mach data is good enough for me.
I understand this is a tall order, but, well, SE is for expert answers - maybe a wonder happens and someone here has it? :)

From Wikipedia, the aerofoil for the wings is NACA 64A-012. If you would like a full airplane, you would need to plot it in DATCOM. DATCOM is a program that is designed to calculate drag, lift, moment coefficient, etc. on an airplane based on coordinates.
So, here is a link to the polar data I got.
If you want more accurate alpha increase, you need to download X-FOIL and learn to use it (quite a tricky program for certain people).
I am afraid the other data is almost impossible to obtain.

What is datcom?


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Why is the pitot tube located near the nose?
The pitot tube located near the nose could be affected by the boundary layer and could increase the error. Then why is the pitot tube located near the nose?

Downvoted because even a bit of prior research would show that not all, or even most, pitot tubes are located on the nose.  For these two examples, I would suspect that it's a location with undisturbed airflow, a short tubing run, and out of the way of ground traffic.

There are several reasons to have the pressure sensors in the front section of the fuselage.

The further aft the more turbulent the airflow is and the thicker the boundary layer caused by the fuselage. This would cause strong fluctuations of the measured pressure and the reading could be inaccurate. Far forward the boundary layer is the thinnest because the boundary layer thickness grows with the distance traveled along the surface.
The position on the nose should be less sensitive to angle of attack and side slip angle changes. Having the sensors on the side of the fuselage would cause significant changes in pressure measurements depending on the aircraft attitude relative to the incoming air.
The pressure sensor in the nose is close to the cockpit instrumentation and avionics computers. Pressure tubes can be short and cannot be disconnected by mechanical forces that easily.
There is no ground equipment moving close to them. Having them further aft could easily damage the sensors during baggage or passenger loading/unloading.
During winter months airplanes have to be sprayed with de-icing fluids. Up front they are not flooded by these substances and are spaced far away from the affected areas.

Some aircraft have the sensors located on the wings. The Cessna 172 pitot tube is one example that comes to mind.

I would add the following reference: E. Haering, “Airdata measurement and calibration,” NASA TM 104316, December 1995.

Perfect answer! in some cases, the pitot tube is parallel to the fuselage, in other word, the pitot is kinda curved as the fuselage (on the nose). Why? does the flow direction is parallel to the fuselage?

The probe is aligned with the local flow,so is normally parallel-ish to the local skjn surface. The pressure sensed varies from the freestream flow away from the body, and so the Air Data Computers have to be calibrated against the true freestream flow with corrections applied. This is Calibrated Airspeed.To get the true freestream flow data, the certification aircraft is equipped with a test boom that places the pitot probe way out in front away from the influence of the fuselage shape, and differences between the test probe and fuselage probe recorded in calibration tables that the ADC uses.

The probe needs to be pointing straight into the local flow because the air needs to enter the probe as close to straight on (from the probe's perspective) as possible.  If the air is entering from an angle, the effective opening size of the inlet hole is smaller, so the dynamic pressure sensed will be lower.  There will be some angle error at pretty much all conditions except one (the one where the probe is straightest into the local flow), so the calibration tables have to account for this error as well.

I imagine pretty much all planes with nose-mounted propellers have the pitot tube on a wing to keep it out of the propwash.

Or on the tail believe it or not.  My own plane (a Pazmany PL-2)) has the pitot at the top of the vertical fin, above the propeller stream. Thorp T-18s also do that.  The problem with it is the pitot comes into the prop wake just above the stall speed (the ASI starts fluctuating; how much depends on the power setting), so it should be about 6 in higher, although Pazmany may have designed that on purpose, because it makes a good visual pre-stall indication, the airplane not having any kind of stall warning system.

@JohnK: Interesting! Quite obvious in this PL-2 photo. I wasn't able to locate a pitot tube in any of the Thorp T-18 photos on Wikipedia.

@Fred Larson The plans showed the fin location but the vast majority of builders or subsequent owners moved them to the left wing.  Don Taylor's round-the-world T-18 has the plans arrangement here: https://www.eaa.org/eaa-museum/museum-collection/aircraft-collection-folder/1968-thorp-taylor-t-18---n455dt

The boundary layer grows in thickness as you move aft on a fuselage. It is thinnest near the nose. A pitot tube near the nose only has to protrude a small distance away from the fuselage skin in order to extend out of the boundary layer and into undisturbed air.

Thank you for your answer, but could you prove your claim by an authentic source?


text:
Should the helicopter be washed after any sea mission?
I was seeing this image:

The caption of this image says (source):

Here a Belgian NH90 NFH returning after a flight over sea. The
helicopter is washed by the fire brigade to remove the salt water...

Should any helicopter be washed after any sea mission? Are those guys washing the engine? If so, should the engine of helicopters be washed after any sea mission?

This question is broadly related to my answer here where you can find more information on corrosion on aircrafts too.

The helicopter shown is an Anti-Submarine Warfare Helicopter. ASW helicopters generally have the ability to detect submarines either Passively or Actively. Passively, sonar-buoys are dropped into the sea and act as ‘microphones’. The returns from these can be triangulated to track submarines.
To achieve this, the helicopters altitude will generally be 1500ft amsl in this role. Unless the winds are very strong salt accretion is minimal. In the active role, the helicopter hovers above the sea and lowers an active sonorhead into the water. The height for this is normally between 40-80ft. The aircraft will stay in this position as long as it takes to establish a 360deg sweep, which is typically less than 5 minutes, or if in contact could remain in the hover for 30 minutes or longer. This process is repeated for the duration of the sortie, which may be up to 2-3 hours.
During this time, the helicopter is experiencing recirculating sea spray. Depending upon the wind / sea state, will determine how much salt accrets (windscreen wipers are required on occasion). The engines experience salt ingestion, which accrets on inlet guidevanes and compressors. As the sortie progresses it is possible to see a reduction in engine performance (the advice for this used to be to find a rain cloud to fly through).
On completion of a days flying over water the engines receive a compressor wash or after a single flight if particularly bad. The airframe will also be washed on a regular basis, perhaps every couple of days. Many bases operating ASW helicopters have dedicated ‘drive thru’ washes. The helicopter will ground taxi over an area with water jets set into the ground and water will spray the airframe and underside of the rotor blades to remove the salt, sometimes known as a ‘bird bath’.

How is this achieved for ship-based ASW helicopters? It would use a lot of the available freshwater of the ship, no?

You’re correct,  however ships that operate aircraft allow for all water usage -the majority of which is taken on in port. The amount used for compressor washes is quite small. Engineers use a dedicated piece of equipment containing compressor wash fluid  / water, sorry I don’t know quantities. Airframe washes wouldn’t use fire hoses when embarked for the very reasons you suggest.

Operating aircraft at sea is a huge subject. As mentioned below, airframes are fully treated on all internal hidden surfaces with an inhibitor, compressor washing and airframe washing doesn’t happen on an ad-hoc basis, they are part of scheduled servicing or daily servicing just like refuelling or checking oil levels etc.

As I recall (this is from 40 years and more ago though) we would wash the aircraft weekly and apply an all over coat of WD40; interim cleaning was done based on daily inspections (That was true for both fixed and rotary wing - a fast jet aircraft on the catapult can suck in significant amounts of spray).

Aluminum is corroded by salt when wet. Anodization and paint or coatings provide some corrosion resistance, but removing any salt is a big help.  Also some components in sea water such as sodium sulfate can cause "hot corrosion" (a specialized high temperature relatively fast corrosion) in many turbine high alloys.


text:
What does "spark plugs appear yellow at the ignition point" mean?
I was reading the DLE-120 engine User Manual and saw this paragraph:

Caution: Running the engine with a lean fuel mixture will cause the engine to overheat and burn the electrode of the spark plugs. Pay close attention to the High-speed Needle adjustment. Running the engine with the proper fuel mixture will make the spark plugs appear yellow at the ignition point.

What does "yellow" mean in "Running the engine with the proper fuel mixture will make the spark plugs appear yellow at the ignition point"?
Does anybody have any experience or images of this phenomenon?

Use the tip residue to evaluate the combustion process
The yellow the manual is describing is the normal condition found in the top left corner:

If the plug is not the yellow/tan shown in the top left, then it will almost certainly look like one of the other pictures. This is a strong hint that what is going on inside the cylinder is not optimal, and points in the direction of the problem.

Thank you for your perfect answer. another question: Is this colors valid for piston engines which use fuel+oil or it is valid for piston engine that use just fuel like car engines?

AFAIK, it is valid for both. Be aware that some of the remedies make less sense for a fuel/oil mixture, though (such as checking piston rings for blow-by due to oil fouling on the plugs).


text:
Who should design the nozzle of jet engines on aircraft?
There is a question in my mind that which company should design the nozzle of jet engine - the aircraft designer or the engine designer?
If you watch this documentary:
BBC Documentary Rolls Royce How To Build A Jumbo Jet Engine
You will see that the engine is designed without the nozzle. e.g. You see something just like the following come out from the manufacturer (Trent 700).

But in fact you will see it on aircraft just like this (Trent 700 on A330).

Which company designs this duct/nozzle/intake? The aircraft designer (in this case Airbus) or the engine designer (in this case Rolls Royce)?

Is your question who does design the nozzle or who should design the nozzle? You asked both in the text but I feel like they are different questions. The later might be opinion based

I suspect there will be some collaboration between the two (as the nozzle partly determines the performance of the engine), but this is primarily the domain of the aircraft designer. Only he/she knows the (aerodynamic) specifics of the integration of the power plant on the aircraft and is able to make a proper trade-off, for example regarding ground clearance.
A textbook example of that is the integration of the CFM56 on different aircraft. The Boeing 737 uses flattened nacelles, whereas the nacelles are circular  on the A320-family. The flattened ones are structurally less efficient, but at aircraft level, it was an easier/better option than increasing the landing gear height. (This problem, by the way, is still haunting the 737-series. A recent innovation featured on the 737 MAX-10 extends the landing gear using a new lever to prevent the tail from scraping the runway on rotation, another problem of a shorter landing gear.)


text:
Do pilot uniforms always include a shirt with stripes?
On airliners, pilot's uniform usually include a shirt with stripes on shoulder. I cannot find examples of pilot without this kind of uniform while in service (either in the airport before departure/after landing or on the flight deck). It seems that during long break they can wear T shirts but use their formal uniform when working.
I fail to see why they should wear such a uniform (wearing a shirt with stripes don't make you a better pilot).
For flight attendants, the uniform reflects the image the company wants to convey. Flight attendant uniforms are thus diverse and different for different airlines. But a pilot's uniform is more uniform from one airline to another.
Do airline uniforms for pilots, which do not use shirts with stripes on the shoulder, exist?

"For flight attendant, the uniform reflect the image the company wants to convey" [sic]. It is no different for pilots, the airline wants them to meet the typical pilot image that most of their customers have in their minds.

Related: What's the reason for pilots wearing uniforms?

@AEhere being disruptive can also be a good marketing strategy (no need to look like what most passengers expect).

@ManuH  how many passengers choose their airline based on how the crew dresses? Or even see the pilots of their flight outside of extraordinary circumstances? On the last dozen or so flights I've been on, I didn't do either, but ymmv of course.

Uniforms are to make it easy to identify members of a group who have a separate function or authority from a larger more random group.  The stripes are to easy to identify the chain of command within this group at a glance.
Most of the time it's all just costume peagentry.
When the shmoozle hits the fan however, being able to identify who's in charge and next in charge and so on, without having to, you know, ask around, becomes a big deal.  That's why the bars.
You won't find a first or second tier carrier in a Western airline without a uniform shirt and rank bars.  I can't find any specific regulations that require that, but it's basically an old convention carried over from the marine world (it's why pilot uniform suits look like naval uniforms), where many of aviation's traditions originate.

The OPs question, though, is: do any carriers (and, by inference, which ones) use a non-traditional uniform.

Thanks.  Added a bit.

I find it very hard to imagine a situation in which it would be necessary for a passenger to be able to differentiate the PIC from FO, or any other dude/gal for that matter. Destination hotel lounge bar would be an exception of course.

Stranded on a desert island perhaps lol?  "How can we make a signal fire from this plastic water bottle, string and a piece of coral?  The Captain will know for sure!"


text:
What is inflated wind speed?
According to NOAA, inflated wind speed is "the true wind speed (in knots) adjusted to improve forecasts of higher wind speeds. Wind speeds greater than the mean wind speed observed are increased, and wind speeds less than the mean are decreased."
From what I understand METARs do not use inflated wind speed as they are a measure of actual wind speed whereas TAFs, etc are forecasts of wind speed so are probability distributions, but instead of taking the mean of those probability distributions (minimize RMS error) NOAA is doing something else. What?

My understanding of that statement is that they take the value the weather model produces and apply a fudge factor because they have experience the model tends to underestimate strong winds and overestimate light ones.

@JanHudec: Confirmed in this thesis.


text:
Other than the 747, are there any other current, recent or planned airliners with a nose door option?
Boeing has recently announced that the 747 program is coming to an end. One of the key features of the freight 747s was the nose door, which facilitated faster loading of freight and allowed the loading of freight that could not otherwise be carried.
Other than the 747 are there any current, recent or planned airliners that have the option for a nose door? will this be a facility that the cargo carriers lose as their current 747s gradually reach end of life? (which granted will be decades after production stops)
I am aware of several other planes with nose-doors but they are either old military-derived types (e.g. the AN-124 and AN-225) or are specialist planes designed for carrying awkward cargo (e.g. the Airbus Beluga and Beluga XL).

You didn't mention the C-5 Galaxy:  https://www.google.com/search?q=c5+galaxy+nose+opening

@abelenky Perhaps because it isn't an airliner? Perhaps because it is neither current, recent, nor planned?

@T.J.L. I think the An-124 neither but it is cited in the question.

@ManuH You've missed point - there's no need for the original poster to list every single plane with a nose door. That said, the An-124 was at least flown in commercial/civilian service, the C-5 never was (nobody bought the non-military L-500 version).

@T.J.L. The confusion came from the word "airliner" you used in your comment to mean "civilian".

Excluding those aircraft in your question the answer is no. The 747 started really as a cargo aircraft, but given that more and more aircraft are available, the cost of development of another cargo only aircraft doesn’t make sense. Cargo operators can just buy old passenger aircraft, and they will continue to as the cost of development of aircraft is enormous, and most airlines at the moment (and most likely for the foreseeable future) are favoring smaller, thinner routes.
Sadly, the 747 and its nose door will be only a sight for cargo airlines soon.


text:
When was the concept of V1 introduced?
When was V1 speed first introduced? Was it the result of a particular accident or series of accidents?

One problem here would be that research of google ngrams of V1 will conflate the flying bomb

@CGCampbell You could search for "Takeoff Decision Speed" or related terms like "Accelerate Stop Distance" / "Accelerate Go Distance".

Google search for "balanced field length".  I'm guessing it started in the 60s.

@JohnK I did some searching: it was already part of CAR 4b § 4b.114 Take-off speeds in the version of December 1953. Unfortunately, I could not find any older versions, so I don't know when it was actually introduced.

@Bianfable I'm surprised it goes back that far. I figured it would have started in jets.

@TomMcW, 1953 is a year after the De Havilland Comet was introduced, and had two accidents where it failed to lift off due to early and excessive rotation.

There were a series of RWY overruns during the days of the first group of jet airliners (early to mid 50's), possibly 3 within a 12 month period. Mainly early rotation resulting in the airplane stalling during the takeoff roll at full thrust. Such accidents caused review of the take off maneuver and birth of the RTOW (Regulatory Take Off Weight) calculations.
A description of 2 cases, 26th Oct 1952 and 3rd Mar 1953

Interesting info; other that taking the word of an unknown somebody on the internet, is there a link that those interested in this question can follow to get more information?

@Ralph J, I've added a link pointing at 2 related occurrences. Would appreciate if you did the same in case you follow up and find a more direct link between actual accidents and the intro of V1. An accident report or 'terms' of a committee given such task.


text:
What aerodynamic data exists for the Yak-130?
This is one of 3 question in "series" - one question split up in 3 to better reward those responding about each aircraft. Other questions: A-10 L-159
Yak-130 is one 3 planes that are used in the ArmA 3 combat simulator, but its aerodynamics modelling currently lacks significantly. I'm planning on writing a short "essay" to developers regarding what and how can be specifically fixed in the flight model, but I'd like to back my research with some hard data. Specifically, I'm interested in any of the following:

L/AoA
D/AoA
Side lift/SA (Slide angle)
Max G/velocity
Flight envelopes

Torques can well be left out - it's not a full fledged simulator, but the above data can give quite a good estimation of high level characteristics already
Are there any good sources on any of the above data? Low-mach data is good enough for me.
I understand this is a tall order, but, well, SE is for expert answers - maybe a wonder happens and someone here has it? :)

Yak-131 is not a real plane and does not exist.

Well, it's a cancelled project which shares airframe with Yak-130, I know. But for this reason, I'd accept data for Yak-130 just as easily.

In such a case it would make sense to request information regarding Yak-130. The never completed Yak-131 was to be essentially the same airplane (when considering your 5 criteria) with better targeting systems and designated as an attack aircraft.

The Yak-130 has a maximum g-loading of +8g to -3g and is capable of executing the flight manoeuvres specific to current operational and developmental combat aircraft, including Su-30, MiG-29, Mirage, F-15, F-16, Eurofighter, F-22 and F-35. This aircraft is of classical swept-wing and empennage monoplane design and light alloy construction with carbon-fibre control surfaces. Kevlar armour protection is fitted to the engines, cockpit and avionics compartment.
Flight angles of attack < 40°.
Speeds:
– level flight, maximum   1 050 km/h
– takeoff (full fuel load)    200 km/h
– landing 195 km/h

Side lift and flight envelope is kind of hard to come by, but I got this information from https://thaimilitaryandasianregion.wordpress.com/2015/10/25/yakovlev-yak-130/.
I would also recommend http://www.airforce-technology.com/projects/yak_130/ as another source to look through. Hopefully I was of any help to you in writing your essay.


text:
Why are most helipads in São Paulo blue coated and identified by a "P"?
ICAO Annex 14, Vol II and FAA (AC 5390-2C) standards establishes 'H' and there is no mention to coating TLOF or FATO.
Brazilian National Regulation (RBAC 155 - ANAC) does not provide any guideline for the blue painting.
I would like to know where this common São Paulo helipad pattern comes from.

Examples:

Google Maps (1)
Google Maps (2)
Google Images

According to the Rules for Heliports in Sao Paulo, the P means that it is private heliport. H for public Heliports,  M is for military. Hospitals use the letter H on a red cross, also when they are private or military hospitals. Examples are given in the pictures below.
It seems that the color blue is not required by the regulations; there are various other colors used in Sao Paulo (see a few examples below I found on Google maps).
I think blue is used mostly because it provide good visual contrast with the white or yellow markings. White paint on concrete can be difficult to see under bright sunlight conditions. The blue color also stands out from the urban environment, making the helipads easy to spot from the air. Try it on Google maps; the blue helipads are relatively easy to find on the satellite view.
This video explains the markings (in Portuguese)

Hospital helipad with H marking and red cross

Military helipad with M marking

Green helipad with circular border and 05 Marking

Concrete helipad with circular border and 05 Marking

Red private helipad

Green private helipad
All images are screenshots from Google maps

In federal level, ANAC (RBAC 155/2018) sets only "H" as identification letter. However, such regulation is obligatory only for private facilities modified after 2018 (if elevated). Hence, the use of "P" might be transitionary.

Do you know what the numbers and arrows mean?

@expeditedescent The triangle is pointing to the magnetic north, the number indicates the maximum allowable weight of the helicopter in metric tonnes and the small arrow(s) are used to indicate the approach path.

I have seen only one helipad so marked, and it was reserved for police operations.

NB My observation was in the continental US, and the pad was marked with a round circle, with a P.  I asked the FBO lineman, and he said it was reserved for police helicopters.  As I recall, it was in the late 1980's and I will try to recall the airport.


text:
Can fake air defence radars be built to fool anti radiation missiles?
Running air defence radar can be a dangerous business because of anti radiation missiles like AGM-88. Radar operators learned to switch radar of trying to prevent hits. Missiles were upgraded to counter this. But what prevents to build multiple very cheap fake radar frequency transmitters? If they cost just as a couple of microwave ovens the cost of losing one will be negligible compared to the missile cost and limited availability. Would such a system of fake radars cause interference to the real ones?

I find this an interesting question, but i don't think it's fundamentally an aviation one

Agree with @Dan. VTC. And as someone who did ECCM testing 30+ years ago, there's no such thing as a cheap fake radar. It needs to behave like the real radar - power, pulse rate, scan rate - which means it costs as much as the real radar.

@Gerry a significant part of the cost of a radar is in the receiver and data processor. A radar signal generator + amplifier + antenna that does not need to be coherent with the receiver is still more expensive than a microwave oven, but much cheaper than a real radar.

@DeltaLima I don't think you could build a credible sim of a targeting radar without a receiver and feedback. The USAF had AD radar sims on their test/training ranges 40 years ago. They weren't cheap. And the purchase price is only a small part of it. Field power, deployment, ops and maintenance, personnel and training all add up. When I retired in the 90's, the trend was toward multiple networked radars to improve survivability and increase performance.


text:
Why are longer wings with foldable wingtips used on the B777X instead of lighter ones with original size?
The new Boeing 777X has longer wings to improve efficiency, but has to adopt foldable wingtips to "fit" into all original airports that host its predecessor.
Tendentially, longer wings would have an higher weight and foldable mechanism surely add extra weight too, but thanks to new materials, new wings should be almost as heavy as previous ones.
For me, in absence of further information and comparisons, it's not so easy to understand why this solution is surely better of simply have lighter wings with original length, that would allow benefits too.

Related: Why has the folding wing option of the Boeing 777 never been ordered? - 2015

Good video explanation on YouTube  here

That video speaks about winglets not foldable wingtips...

This explanation is given here :

The wing of the 777X is based upon the design of the 787’s wing. It
has less of the sweep of the 787 but 10% more surface area (increased
from 4,702 to 5,562 sq. ft.). The re-shaping has led to a higher
lift-to-drag ratio, which(and) in turn increases usable fuel bulk from
320,863 to 350,410 lb. As a result, the type will have a range of over
14,000 kilometers (8,699 miles).
Boeing’s motivation for its including folding wingtips within the
design was not wholly steered by fuel economy. With a fully-extended
wingspan of 71.8 meters, the new 777X falls within the ICAO’s
aerodrome Code F. But with raked and folded wings (and a span of 64.8
meters) the type can comfortably arrive at gates designed for Code E.
Aircraft in this group includes the current 777.

So not only are they looking for more surface area and aerodynamic efficiency, they need to house more fuel to give it an extended range.

I assume they are not storing fuel in the foldable wingtips, but the rest of the wing now has a greater volume and can store more fuel?

@rob74 That's how I read it.

Consecutive units conversion! 436.83 m², 516.73 m², 145.541 t, 158.943 t.

There's a trade-off between saving weight and improving lift-to-drag ratio.
In the case of the 77X, the efficiency gain of the improved lift-to-drag ratio of the longer wing outweighs the potential weight saving of the shorter wing.
In other words: the drag reduction results in more fuel savings than the weight reduction would.
For long-range aircraft, it typically pays off to add some weight to gain better fuel burn efficiency (heavier but more efficient engines) or lower drag.  Both result in lower fuel burn in cruise, and thus in weight savings on the fuel you have to take along.
Short-haul aircraft on the other hand spend relatively more time climbing, so they optimize a bit more towards low weight and less towards cruise efficiency.


text:
Checkerboard painted on fuselage of Boeing test aircraft
What is the purpose of the four square block checkerboard painted on the aft fuselage of Boeing's flight test aircraft?  It is either break in markings for fire rescue or some sort of optical measurement for speed, distance associated with flight testing, I believe.

the checkerboard mark allows accurate indication of the position of the plane using cameras as the plane flies by. by tracking the movement of the checkerboards between frames of a series of camera shots, the plane's speed, roll rate, acceleration, etc. can be measured.

A little hairsplitting if you will, but I‘d say these parameters can be calculated rather than measured... great answer though!

indeed, but photogrammetry is a good failsafe in case your telemetry links fail.

Yes, of course! What I mean is that with photogrammetry, you calculate the rates and accelerations rather than measuring them (you measure pixel displacement and then derive test aircraft flight mechanics parameters)

I have added a link to a picture (see above) that shows what I am asking about.  I appreciate your answers.  Is this still used today, or has it been replaced with telemetry?

@Kim It's not telemetry per se but accelerometers (AHRS) became much smaller, cheaper, and accurate, and GPS became available. Though some test flights still require chase planes, in general its cheaper, easier, and safer to rely on on-board instrumentation. Also in the old days, you'd do photogrammetry by manually measuring the image. Now we have computers that can in real-time correlate natural features on the plane, exactly the same principles as AR apps on your smartphone.


text:
What is the youngest age allowed to fly any sort of plane in the USA?
I have wondered this for quite some time, but what is the youngest age to fly any sort of plane in the USA? Does it also vary on what type of plane you're flying? (Commercial, Private, Training.)

Would a glider count as a plane? If I remember right, the minimum age to fly solo in a glider is different from an airplane.

@TannerSwett I think a glider would count as a plane.

The "Child Pilot Safety Act" was brought into law following a high profile accident with a child pilot.

Does "airplane" mean only including what the FAA calls "aircraft", or can an ultralight airplane (which the FAA calls a "ultralight vehicle") be counted as an airplane?

The easiest way to figure this out for the US is to look at 14 CFR Part 61

§61.83   Eligibility requirements for student pilots. To be eligible
  for a student pilot certificate, an applicant must:
(a) Be at least 16 years of age for other than the operation of a
  glider or balloon.
(b) Be at least 14 years of age for the operation of a glider or
  balloon.

That is the age at which you can solo. Lots of airplane pilots take lessons and solo on their 16th birthday. I don’t follow the gilder world and balloon world, but I assume lots of kids solo on their 14th birthday.
To get a license you must be a bit older:

61.103   Eligibility requirements: General. To be eligible for a private pilot certificate, a person must:
(a) Be at least 17 years of age for a rating in other than a glider or
  balloon.
(b) Be at least 16 years of age for a rating in a glider or balloon.

One can be younger and fly with an instructor, altho the hours may not be loggable if too young. If one see out the front, one can fly. See the EAA Young Eagle program as an example. Over one million kids have been given rides, and many have taken the controls during the flight. Flying with a Private Pilot, their time is not loggable, but they enjoy the flight none-the-less.


text:
How do handling characteristics depend on flying with a full vs. an empty tank?
Modern aircraft are capable of carrying a lot of fuel to achieve extra-long range; we're at a point where nearly every pair of destinations can be reached non-stop. Carrying so much fuel imposes limits on take-off and landing weight, so the proportion of fuel to airplane weight is not negligible.
I'm wondering how the handling characteristics of airplanes change as the fuel is used up. Do the pilots feel that the airplane is lighter towards the end of the flight? Can they do faster maneuvers with nearly empty fuel tanks?

Do you mean airplanes in general, or just airliners?  Certainly my Cherokee climbs better with partly full tanks. (Indeed, I almost never fill them completely, just "to the tabs" which is about 80% of capacity.)  I wouldn't care to depart from a high elevation field on a hot day with full tanks.

@jamesqf As I was unable to find much information on either, both are applicable! :-)

Datapoint for interest: NOT at all a modern aircraft :-). The Me262 could fly on one engine only when close to out of fuel Losing an engine when more fully fuelled meant 'going down" was imminent. || This based on comments from Pierre Closterman in one of his books. PC was not the most reliable of sources so that MAY not be true, but probably is. [He says he chased an Me262 and shot out an engine (or it had lost an engine) but it managed to return to base and evade him despite briefings stating it could usually not fly on one only engine.

The later part of the question "How do handling characteristics depend on flying with ... an empty tank?" brought me here as I wondered if it was related to  Running out of fuel.

@chux-ReinstateMonica Well, if it was the case of completely empty tank, there would be some obvious differences such as that the engines would not work ;-)

All aircraft are subject to performance changes due to fuel burn, and since weight, lift, thrust and drag are all tied together for every aircraft in the same way the changes scale nicely. Let's look at some extremes:
One of the most interesting examples of this was the Concorde. Since the Concorde flew ~20K above every one else in the sky in those days it didn't have the same altitude holding restrictions that regular airliners (or any IFR airplane) has. The Concorde was give a block altitude basically to do what it wanted up around 50,000 feet (ca. 15 km). Since it burned quite a bit of fuel at Mach 2.1 and gradually became lighter during the flight the pilots let the plane slowly drift up to gain efficiency as well as gliding distance if needed.
The Concorde also used its many fuel tanks to trim the aircraft as well as cool the nose cone. Fuel burn was closely monitored and constantly pumped around to ensure the aircraft remained in trim.
Even the dinky Piper Archer I fly is affected by partial tanks. If I fly the tanks from full to VFR legal reserves, the CG moves forward a full inch. Granted this does not seem like a lot you will need to trim to compensate for this throughout the flight. You will also be landing a full 240 LBS lighter which is about 10% of the total weight from takeoff. If you come in hot and high you can get yourself into trouble.
Yes you can feel it, generally pilots are not going to do “faster” maneuvers but the maximum G load may change (see your aircraft's POH for more info).
Any smart pilot should practice flying their aircraft at various fuel loads to understand the differences it makes in performance and handling. Some aircraft with things like tip tanks or auxiliary tanks even have fuel burn limitations that define where the fuel is to be burned from and in what order, again going from something as small as a Bonanza all the way up to the Concorde as discussed above.
Just how much can the handling change? Assuming you did your due diligence in pre-flight and calculated your W&B on both ends of the flight accounting for fuel burn to ensure you are within your CG limits the flight should occur with in the limits of the aircraft's POH and generally speaking within operable limits of the airframe. FAA certified aircraft have control force limits so even at the extents of the CG range you should be able to trim the aircraft to handle “normally”. You will likely notice pitch differences (at either extreme) as well as various performance number differences.

Modern gliders are an interesting data point regarding this. A competition glider carries water in its wing tanks to increase weight. This betters performance at high speed, which is essential for competition when conditions provide strong lift.
The pilot can release the water at will, and the tanks can be emptied in a few minutes. This happens in competition every day, either when you are arriving (to land without the extra weight) or sometimes mid-flight when conditions are worse than expected.
So, taking as an example a Ventus 3:

This glider, with pilot included, weighs around 380kg. It can carry up to 212 litres of water in its wings, for a maximum gross weight of 600kg (it also carries a few litres in the tail for cg purposes).
In summary, the pilot can change the weight of the glider from 600kg to 380 kg in some 4 minutes (meaning a 38% change in weight!). This makes the change very noticeable. When empty, the glider is more "feisty", both in that it reacts more to turbulence, and in that the commands (the ailerons, especially) are way more effective.

Aircraft performance does change with weight. Not only does takeoff weight and balance need to be considered, zero-fuel weight and balance does as well. Many key performance metrics depend on this, like takeoff and landing speeds and distances. Climb performance and range are also affected. Inflight, Va (maneuvering speed) is very dependent on weight. The speed at which you can fly while putting extreme loads on the airframe from abrupt maneuvers or turbulence actually decreases as weight decreases.

Alone in an A36 Bonanza from central Florida to North Central Indiana, I flew on one load of fuel by decreasing the throttle gradually as I burned fuel to maintain a constant airspeed.  The aircraft wanted to speed up as it lost weight.  So, yes the aircraft will fly differently as the fuel is used.

Something else that changes with a change in CG and/or weight is your stall speed. There is a good article from AOPA here: https://www.aopa.org/news-and-media/all-news/2020/march/flight-training-magazine/aerodynamics-stall-speed


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What's the rationale for requiring ATP applicants to be at least 23 years old?
The FAA requires pilots to be at least 23 years old to acquire an ATP. But what's the rationale for this rule? I can understand why has to retire at the age of 65 but why can't we have an 18 year old captain flying a jet?

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(23 is way too young, it should be 25 or more.) Note as a curiosity, male brains mature much, MUCH, later than female brains. (Google the research.)  If 18 year olds or 20 year olds were to be allowed, it's inconceivable males would be allowed, it would only be female pilots.

@Fattie how do they make sure immature 25 year olds don't become pilots?

@JonathanReez How do we ask rhetorical questions?  They don't. The fact that cutoffs are a gray area, is unsurprising and a normal part of the world.  In most countries you can't drive a car until you're 15.  Are there 12 year olds who could perfectly drive a car, yes; are there 30 yr olds who are way too immature to drive a car, yes.  There is no amazing mystery, surprise or confusion in this.  Flying a plane has stunningly drastic consequences if you fuck up; if you fuck up driving a car the consequences are trivial (at worst you might kill 3 or 4 people). No great mystery.

Another related example, I believe in the US the air force has a simple height limit (something like 5'5" to 6'5" and that's it).  It's a gray area (like all limits), but "gray area" does not imply "it's best to have no limit".

The age requirement for an airline transport pilot has been in place since at least 1937.  You can search for CAR Part 21 on the FAA DRS website. https://drs.faa.gov.

I tend to agree with the other answers as to the mental capacity to make complex decisions.

FAA 8900.1 Volume 5 Chapter 3 Section 2 (official guide for examiners) states the following:

5-837 A. Manipulative Skills. The manipulative skill standards for the ATP Certificate are the most rigorous of all pilot certificates issued. The skills requirement for the ATP Certificate and for other certificates differs not in the tolerances allowed, but in the degree of mastery required.  The applicant for an ATP Certificate must demonstrate the ability to operate the airplane smoothly under a complex set of circumstances

B. Flight Management Skills. The term “pilot in command” implies that the pilot is the leader of a crew and bears the final responsibility for the safe conduct of the flight. This standard, more than any other, distinguishes the successful applicant for an ATP Certificate from those holding other grades of certificates. The ATP flight test must not be limited to a simple demonstration of a series of events. An ATP applicant must demonstrate a mastery of complex
problems, good judgment, situational awareness, Crew Resource Management (CRM), and leadership skills.

This is actually quite interesting, since I don't think neurological research regarding the development of the brain was at the level I describe in my answer in the 30's. So while the rationale may have been the same, I'm not sure there was as profound scientific evidence back it then.

@Jpe61: That viewpoint is kind of putting the cart before the horse — it’s like saying it’s interesting the Greeks used hemlock for execution since they didn’t understand the chemistry of toxic alkaloids.  People have known since time immemorial that many aspects of adult competence — “maturity” — are typically still developing fast through teenage years, and slow down or plateau only in peoples’ twenties. Modern science has helped us quantify the phenomenon and understand its causes, but the basic outline of its effects were known perfectly well in the 1930s, or indeed the 1390s.

My point was (I worded it poorly) that they already knew the subject, but evidence we have now strongly backs it up. They may have had some scientific evidence back then, but I haven't dug that up.

Brain development.
An airline transport pilot has to deal not only with by-the-book situations, but also with situations that aren't going by the book. If they didn't, we'd have them replaced by AI years ago.
To reach ATP requirements by 18, your life has to go perfectly. Born in a pilot family, trained early, got your hours in minimum possible time. That ensures the ability to manipulate the controls - the ability the autopilot has as well. It says nothing about one's ability to handle stress and uncertainty.
Being 23-65 years old doesn't guarantee that ability, just as being 35-65 doesn't guarantee the ability to handle presidential duties. But being outside that range greatly increases the chances of not having that ability.
Starting at 23 also gives time for a college degree, which helps prepare one for the amount of paperwork that comes with being an airline pilot. The captain especially isn't just an aviator - they are also in command of both flight and cabin crew once on board, and ultimately responsible for the passengers. The first officer has fewer command duties (until 2013, only captains needed an ATP), but they have to be able to take them over as well.
It's discrimination, but it's fair discrimination, based on what the job entails.

Is 35 the minimum age to be president?

@Cloud you do not need brain development to be a president: you just need to understand which lobby groups succesfully put you up there. Even a teenager can understand and act accordingly to that ;)

I know it was just a joke, but "discrimination" (in the sense it is used in 99% of cases these days) means unfair discrimination. Nothing about having a clear age requirement set by regulation is unfair. It would be unfair if there were no public regulation, but a company denied applicants based on their age without telling them, while pretending that it is not discriminating based on that. Or if a company would fire a pilot due to age (before reaching the official 65 years). So it is in fact not discrimination (in the negative connotation). scnr

35 is the minimum age to be President of the United States. This is a requirement mandated by the Constitution.

@AnoE it really goes beyond regulation and is more about when you are allowed to discriminate in employment hiring on the basis of protected classes (old age, sex, national origin, race etc).  A job that requires lots of heavy lifting would be allowed to set requirements (eg must be able to easily lift 100 lbs) that amount to de-facto discrimination on the basis of sex, but such a requirement would be grounds for an easy lawsuit if it was a cashier job.  Though it's true that for pilots it's spelled out in law and regulations, it's a special case of a very general thing.

@barbecue And yet, if recollection serves correctly, brain development was not complete with a recent one you had...

@EndAnti-SemiticHate The bar has been permanently lowered, and I anticipate a root vegetable winning the presidency sometime in the next decade.

@barbecue, yes, some root vegetables are remarkably mature, especially toward the end of their winter in the root cellar. :)

@barbecue Think it might be an improvement?

I'm going to set aside the "18 year old captain" and approach this matter  form an "18 year old airline transport pilot" point of view.
It is well documented in medical science that an 18 year old is still cognitively undeveloped. For example the folowing article quite nicely sums up most of the subject: Maturation of the adolescent brain
While it certainly is true that individual variation is great in this matter, for the sake of simplicity a single age restriction has been set. 23 is not arbitrary, as statistically human brain, and namely the prefrontal cortex which would be the most important part in most cognitive and social functions reaches maturity at the age of 25. Considering that one can assume that most of the candidates for ATP licence are sufficiently developed by the age of 23, while people at the legal maturity age of 18 are still "cooking" so to say.
Difficulty with allowing a 15 year old (derived from comment below, used as an extreme example) take on extrememely demanding tasks is, as I tried to describe in my answer, that a person at that age is not fully "formed". They will evolve, and not necessarily into a good direction. This development is not something the person can control themselves, as it is to a large extent hormonally driven. It is by far much safer to see how things turn out, that is to wait until the person's brain develpoment is likely to be advanced enough to assume certain stability. Allowing a larger range of ages would necessitate streunous and expensive screening processes, which themselves are not foolproof.
Main point would be, as stated in the aforementioned article:

Furthermore, the adolescent brain evolves its capability to organize, regulate impulses, and weigh risks and rewards; however, these changes can make adolescents highly vulnerable to risk-taking behavior. Thus, brain maturation is an extremely important aspect of overall adolescent development, and a basic understanding of the process might aid in the understanding of adolescent sexual behavior, pregnancy, and intellectual performance issues.

From a personal point of view, and having 50 odd years of observation of life, I can safely say that only a diminshingly small fraction of 18 year olds can be considered mature in the sense that is necessary if one was put in charge of hundreds of lives. Aviation industry in general is extremely focussed on risk mitigation, and setting this requirement is simply one way of avoiding unnecessary hazard. Surely there are a handfull of candidates that will suffer  subjective injustice because of this, but as a whole, everybody wins.
As an endorsement to Michael hall's excellent answer, while it certainly is possible to accumulate the hours requiered for ATPL at a very young age,it simply is not the hours that make you competent. There is plenty of evidence that quickly, even frantically gained experience is more likely to produce complacency rather than competency. Rushing experience at a relatively young age carries the risk of distroting the develoment of the prefrontal cortex. It is better to learn slowly and over time, gaining a broad range of experience of different situations and learning from a large pool of peers and seniors. This will enable the brain development to keep up with the learning, and create healthy strategies.
As a sidenote, from the current scientific point of view it actually is strange that people are considered to be fully legally liable at the age of 18.

I thought the whole notion that the brain finishes developing (i.e. stops developing) at some point is a myth and has been debunked?

The development in described in my answer is far more profound than the one going on through later stages of life. Currently it is commonly accepted that the actual personality of an individual generally continues to develop  trough life, althoug it is considered to mostly stabilize between the ages of 35 to 50. Again, variation is great, but anyway major development in capabilities and personality stem from the functioning of the neurons and the networks they create. So yes, the brain does develop througout most of the adult life.

I found this "prefrontal cortex which would be the most important part in most cognitive and social functions reaches maturity at the age of 25" very interesting. Can you provide a scientific reference? @Michael can you provide a scientific reference for its debunking?

@EarlGrey the article I linked in the answer discusses this, and as an example it presents this graph: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3621648/figure/f3-ndt-9-449/

@EarlGrey and for a super interesting example case google Phineas Cage.

One would hope, @Michael, that one's brain does not stop developing (though for many, it seems development stopped after 4-6 years, maybe 15...). The point is that it has developed enough (in general) by age 23, to help minimize the risks associated with being a pilot of an aircraft and being responsible for 10+ other people's lives.

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@Michael "I thought the whole notion that the brain finishes developing (i.e. stops developing) at some point is a myth and has been debunked" that's super weird and totally bizarre, where did you hear that?  (You might be thinking about "the mind" or "emotions" or something?) Obviously your skeleton, your brain, and your other systems grow  (during "childhood") and then reach completion at some point (ranging from 14 to 25 depending on the "bit" in question, and it's wildly different for men and women. I guess you must be thinking about "the mind" or "emotions" or something?

Same for @FreeMan , you may be thinking about "maturity" or "soul" or something?  the brain is just an organ like say6 the heart or kidneys.  Look in a medical textbook to see when each "bit" typically is finished growing.

Outside of brain development and any issues of emotional maturity, there is a strong case to be made for confidence and competence due to quality and breadth of aviation experience gained over a longer duration of time.

It normally takes years to accumulate the flight experience to qualify for an ATP.  For example, it took me roughly a decade to get the hours and an ATP.  During that time I made countless approaches in all kinds of weather conditions, and logged thousands of landings.  And grew tremendously in the process.
For comparison, running straight math, if you flew 8 hours a day 5 days a week you could have 1500 hours in 37.5 weeks.  That's it, less than a year.  And unless you are working the pattern hard, you'd have far fewer approaches and landings and likely a lot more time at cruise where the workload is much, much less.

So theoretically a pimply 17 year old could get a PPL, and a year later turn 18 and have the hours needed for an ATP.  Do you really think the meager wisdom and experience gained in cramming so many hours into such a short time is at all comparable to someone who has paid their dues over a longer period of time?
Given the same number of hours, would you hire a pilot with 10 years of aeronautical decision making experience, or one year?  And regardless of what you might do, it's worth mentioning that airlines weigh tactical military flight hours differently than transport military hours.  There's a reason for that, and the same logic would apply to a very young ATP.
Sheer hours spent airborne isn't the only, or even the best measure of experience.  It's just the one people tend to pay the most attention to because it is one of the easiest to measure, and there is a presumed correlation to other desirable characteristics of a pilot.

What stops a somewhat-less-pimply 22 year old from gaining the 1,500 hours using the exact same strategy?

Nothing. But the pimples clearing up provides some small comfort to passengers disturbed by the excessively youthful appearance of those they entrust their lives to.

The Colgan Rule was a disaster of unintended consequences having the exact opposite effect to what was intended. I used to know a number of Regional Chief Pilots in my job, and they would complain bitterly about how the 1500 hr requirement, completely arbitrary, blew up their recruiting pool, forcing them to turn away superstar candidates with 800 hrs in favour of midwits with 1500. Candidate quality was actually declining, and they were having to add sim sessions to type courses for new hires as failure rates rose.

@JohnK, Interesting, but doesn't that speak just as much to hours not being the best measure of skill as to age?

@MichaelHall I think neither age nor hours flown are a reliable indicator of anything. I've seen extremely reliable 16 year olds and 45 year olds who were a complete mess.

Anything?  That's a pretty absolute statement!  Anyway, when hiring for any profession some objective measure of personal experience and competence appropriate to the position is appropriate.  What do you suggest?

@MichaelHall It wasn't a direct answer to that particular question, which is why I just posted as a comment. It points to the fact that operators, once a candidate has a minimum exp level and a decent skill level, consider a number of psychological and personality factors as priorities. Indirectly, the minimum age requirement could be thought of as helping address that I suppose, especially since suitability for command is one of the key priorities.


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Why does the Boeing 777X have a flight deck similar to the 787 and not to the previous 777?
Almost 3 years ago I posted this question, Why didn't the A330neo and A320neo share the cockpit of the A350?, and short answers were:

"it's what the market wanted"
"there is a huge disadvantage to drastically changing the cockpit when going from an A320 to the A320 NEO or from a B737-300 to the B737-700, or 737 NG to 737 Max, and that has to do with the existing fleets."

Ok, I surely understood those ones, even if I specifically cited examples like complete transformations of B737 flight desk in 40 years history (explained as well in the second answer, thanks to sort of "compatibility mode" for old pilots).
I recently discover that new B777x has a flight deck almost equal to B787 (here a video) and not to previous generation B777 so argumentations explained so well in past answers are not suitable for this model.
Generally it seems that Boeing is "more courageous" in their updates than Airbus that seems more traditional (I am an Airbus fan but in this case, this seems the truth).
Anybody knows why B777X is so different from the original model, considering that efficiency seems increased of about 15%, something like difference between A330 and A330neo, or A320 and A320neo that share more things with original models?

A320 entered service in 1988 with first flight in 1987, almost 27 years before first flight of A320neo but... new models share almost the same cockpit...

The reality is that the 777X is not all that different from the 777 when considering cockpit procedures or 'user interface'. What is different is the hardware platform(s) that are used.
I worked for a supplier to Boeing for the 787. The stated goals for the 787 from Boeing were fairly straightforward. The design shall require a maximum of 5 days transition training for 777 pilot with a goal of 1 day. On the support side, there was a push to greatly reduce maintenance and upgrade costs. These are driven by the hardware and system architecture.
So the big change with the 787 was moving from the Honeywell AIMS and A629 based network to the Collins/GE A651 and A653 based Common Core System and A664 based network. The result of that platform change is why the flight decks look so different and that's what you see in the videos.
I can say with authority that in the 787 design our overriding directive was to make it look and behave like the 777. While a keyboard and a window on a widescreen display looks different from a control and display unit (CDU), the key functions and display behave the same.
So now with the 777X, the hardware is an evolution of what's in the 787. It uses the same basic open architecture and also follows the tenet of minimal changes that will require crew training.
So ultimately, the 777X is operationally similar to both the 777 and 787 while the hardware and software infrastructure follows the 787.
The impact of training is significant.  As explained to me by a United rep, when one senior captain retires it generates 10 to 15 training requirements as crews move up in the system. Every day of training costs them a lot of money.

this seems to come from a pretty reliable source. Thanks!!

Very interesting but my doubts, in a such way, remains... I understood your reasonable argomentations for Boeing but why this should not be true also for Airbus with their A320/A330neos? Same considerations made about different interface for almost same operability should apply also to Airbus models in that way for a company could be easier to transition a crew from an A350 to an A330neo and viceversa, like for Boeing from B787 and B777x.
In other words, what are differences that push Boeing in this direction and Airbus in the opposite?

That would be a new question, but here's one possible thought: Both OEMs have the same underlying issue. Commonality across the fleet is good. Both pilots and maintainers like commonality as it simplifies their lives. The down side is that at some point due to technology or market forces something has to change and as soon as you introduce change, you're no longer common. How they manage that change depends on the culture and priorities of the business. Boeing and Airbus are two vastly different companies so there's no reason to expect them to manage the issue in a similar manner.

Not quite sure this is the actual reason, but you have to consider why they keep things the same (or not). There are two main reasons I can see:

Pilots type certification. A pilot certified on a given "type" can fly any plane of that type, with (sometimes) just a little bit of additional training to cover the (supposedly) few differences between various aircraft of the same type. If a new aircraft is not the same "type", then pilots need a lot more training to be certified on that new aircraft. This takes time and money.
This is actually one of the root causes of the 737 Max debacle: Boeing wanted the new aircraft to be the same "type" as the previous models (which were the same as the previous one, and the one before), because airlines wanted that as well. So they tried to make the 737 Max behave like the previous 737s even though, given the positions of the engines, it didn't really, which brought them to introduce the MCAS system, which itself made things even more different.
Parts commonality. Parts are replaced on aircraft every single day. Having a stock of parts (and associated procedures) that can be used for any plane of the same type is a huge plus. No need to start stocking spares for different types all over the place.
Of course there WILL be parts that change (otherwise it would be the same aircraft!), but the more flight-essential components are common, the better.

So when you have an aircraft with several thousand airframes already in the market, with all the pilots trained on that aircraft, all the spares for that aircraft, there is a strong incentive to keep the same type. When you introduce a brand new aircraft that is substantially different, airlines will have to train pilots and start stocking parts for that new aircraft.
This is one of the reasons new entrants have a hard time picking up pace.
Now, back to the 777X. So it would seem obvious that being compatible with the 777 would be a huge boost. But there are just over 1600 aircraft of that type delivered (with a few hundred more still in the order book). This is far less than the nearly 5000 of the 737-800 alone, over 10000 of the many 737 variants, or the over 9000 A320s. Also, 777s fly to a lot less destinations (they're used mostly for large-capacity long-haul), so the number of places where you need spare parts is reduced. So the incentive is not as strong.
Factor in the fact that there are nearly a thousand 787s delivered, and over 500 more on order, and you see that having things in common with the 787 rather than the 777 may not be not such a bad idea.

I fully agree, especially considering that the 777 and 787 share a type rating (at least in Europe).

Thank you for your answer but same considerations should be made also by Airbus for their A330neo (that for orders numbers is more comparable to 777 than A320) but instead in that case they prefer to remain "classic". Just courious about different reasond by two manufacturers in almost same conditions

@LucaDetomi an A330NEO is more likely to replace an A330CEO (and same for the A320CEO/NEO) in a fleet than it is to operate alongside a A350XWB with the same crew operating across both aircraft, so it makes more sense to keep the A320/A330 cockpits familiar to the crews that will be flying them than update them just to bring it in line with another product.  Conversely, the 787 and 777X are complementary models (with the 787 sitting far enough below the 777X that they dont conflict) and many fleets are intending to use the same pilot pool for both aircraft.

@LucaDetomi this wont have been an off-the-cuff decision, this will have been a decision made after countless meetings, studies, conversations with customers and study groups etc etc etc.  Airbus didn't just go "lets save some money here and not be courageous in updating our cockpits..."


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Was wood used in the construction of the TU-144?
This image the Yegoryevsk crash of the TU-144 CCCP-77111 appears to show a part of the wreck made of wood:

(picture source)
The inside looks like wood slats with rafters. Wood is sometimes used in airplane construction and has pretty good constructive properties, so I don't want to dismiss the idea a priori as crazy. Was it the case?

sure, it is brownish, but that looks like standard metal construction to me

Surely it was used in constructing the airplane - where do you think they got (some of) their jigs, stands, workbenches, manufacturing building, etc. etc. from?

Wikipedia has a brief note on the crash in Yegoryevsk. That photo looked so much like France in the 70s I was fooled for a moment.

You're looking at a typical metal wing's innards with stringers (small lateral stiffeners made from aluminum angle) riveted to aluminum sheet, and the remnants of wing ribs also attached.  The colour is zinc-chromate primer which ranges in colour from bright green (epoxy zinc chromate), to olive drab, to, that that case, yellow/brown.
There is no wood there.  If any wood can be found in an airplane like the  TU-144, it will be in the interior finishings or panels, or possibly internal bits or fittings that are usually made from plastic, say like a saddle that holds some kind of cylinder in place (in lieu of a plastic or rubber material).  But as far as that picture is concerned, you are definetely looking at metal.